1. Field of the Invention
The present invention relates to touch panels and display devices using the same and, particularly, to a carbon nanotube based touch panel and a display device using the same.
2. Discussion of Related Art
Following the advancement in recent years of various electronic apparatuses, such as mobile phones, car navigation systems and the like, toward high performance and diversification, there has been continuous growth in the number of electronic apparatuses equipped with optically transparent touch panels in front of their respective display devices (e.g., liquid crystal panels). A user of any such electronic apparatus operates it by pressing or touching a touch panel with a finger, a pen, stylus, or another like tool while visually observing the display device through the touch panel. A demand thus exists for such touch panels that are superior in visibility and reliable in operation.
At present, different types of touch panels, including a resistance-type, a capacitance-type, an infrared-type, and a surface sound wave-type have been developed. The capacitance-type touch panel has the following advantages, such as high accuracy and strong anti-jamming ability, thus have been widely used.
A conventional capacitance-type touch panel includes a glass substrate, a transparent conductive layer, and four electrodes. The material of the transparent conductive layer is selected from a group consisting of indium tin oxide (ITO) and antimony tin oxide (ATO). The electrodes are made of metal and separately formed on a surface of the transparent conductive layer. Further, a protective layer is formed on the surface of the transparent conductive layer facing away from the substrate. The material of the protective layer is liquid glass.
In operation, an upper surface of the touch panel is pressed/touched with a touch tool, such as a finger, or an electrical pen. And visual observation of a screen on the liquid crystal display device provided on a back side of the touch panel is allowed. In use, due to an electrical field of the user, a coupling capacitance forms between the user and the transparent conductive layer. For high frequency electrical current, the coupled capacitance is a conductor, thus the touch tool takes away a little current from the touch point. Current flowing through the four electrodes cooperatively replace the current lost at the touch point. The quantity of current supplied by the four electrodes is directly proportional to the distances from the touch point to the electrodes. A touch panel controller is used to calculate the proportion of the four supplied currents, thereby detecting coordinates of the touch point on the touch panel.
However, the material of the electrodes such as metal has poor wearability/durability and low chemical endurance. Further, when the substrate is deformable and made of soft material, the electrodes formed on the substrate is easily to be destroyed and break off during operation. The above-mentioned problems of the metallic electrodes make for a touch panel with low sensitivity, accuracy and durability. Additionally, the cost for forming the metallic electrodes is relatively high.
What is needed, therefore, is to provide a durable touch panel with high sensitivity, accuracy, and brightness, and a display device using the same.